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wich a\f on e85?

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  • wich a\f on e85?


    Thanx for a nice site\forum

    I have a saab 900 turbo 16v with autronic smc

    I use innovate lm-1 with gas calibration

    What a\f is recommanded on a turbocharged enginge with e85 on following load pressures:

    0.5 bar
    1.0 bar
    1.5 bar
    Saab 900 t16 Autronic SMC ++

  • #2
    Morti, You can use this
    Robert Jansson


    • #3
      Yes i know about the a\f calc..

      But i have heard it is possible to run a bit leaner on e85 because e85 cools down the engine more then ordinary gasoline

      Someone with e85 mapping experience here?
      Saab 900 t16 Autronic SMC ++


      • #4
        I do indeed see more power running a little leaner with the E-85.

        Leaving the Innovate LM-1 set to gasoline is fine. You simply tune to similar values under heavy loads.

        .5 bar I would tune to 13.0:1
        1.0 bar would be 12.2:1
        1.5 I would be 11.8:1

        As you see, it is only a little leaner. I have seen power gains all the way up to 12.5:1 at 1.7 bar, but this was a bit of an exercise on the dyno and I did richen back up to 11.6. I lost power but I still wish to keep a large margin of safety on the customer car.

        My personal car was running as lean as 12.6:1 under 1.2 bar by accident when I had miscalculated my charge temp estimate. But the ambient air was very cold (O celsius) and this may have helped allow the lean mixture to resist detonation.


        • #5
          Ok thank you!

          Do you have any idea on how much i can increase the ingnition timing with e85?

          I approx run theese values in my map with 99 octane gas:

          @ 0-100 load = 25 degree ignition angle
          @ 200 load = 15 degree ignition angle
          @ 250 load = 9 degree ignition angle
          Saab 900 t16 Autronic SMC ++


          • #6
            I also have a SAAB 900 16v, but it has a slightly larger turbo and the Normaly aspirated compression ratio pistons.

            I spent some time on the dyno today, I did not do any power tuning, I was doinjg an experiment to find the best AFR for economy with timing optimized for that AFR. (ALL AFR's noted here will be on the gasoline scale even though i was using E85, which at this time of the year here is supposedly E70).

            I logged my rpm and load at about cruising speed on the highway at 3000 rpm fith gear , so that i could go to the dyno and then get an idea of my HP required at cruising speed.

            I went to the dyno and loaded the car to my cruise conditions, and noted the tractive effort (say 30 lbs).

            I then loaded the car at this point at different AFR's and then exoperimented with the timing with fixed AFR until i found the timing that used the lowest msec of fuel while still making 30 lbs.

            I repeated this for different AFRs.

            The results: (only listing the least efficient tested to and the most efficient)

            3000 rpm, 30 lbs tractive

            manifold kpa=about 55 for all

            AFR 15,best advance=28,msec required=2.27

            AFR 16.8,best advance=40 ,msec=2.07

            i experimented past 17:1 and between 15 to 16.8, but 16.8 was the best
            timing seemed very critical 1 degree either way lost 3 lbs or so tractive force.

            i did not do any power runs , but generally it supposed to be less timing needed for e85 because it burns faster than gas,however because of the octane rating less retard is needed under boost,and it seems you can run alot leaner...? so in a nutshell the theory is you can run less timing until you were knock limited in your gas tune, but then you may be allowed more timing than in the gas-knock limited areas under boost. That is to say mean best timing is less with e85, but less retard is needed to prevent knock...this is the theory anyway it will be maybe 6 months until i do a similiar test for power tuning.

            Right now i am mapping my engine as TPS/LOAD this way I can target economy or Power AFR dependent on TPS postion (driver intention) rather than just load. For instance on highway cruise and a moderate hill you may near 100% load and would rather target leaner, beacase you are just trying to maintain cruise, not accelerate, When at other times you are at the same load site but want max acceleration. by putting "wrong" values in the fuel table at less than 100% TPS you can have econmy AFR's, yet when you go to 100% TPS it can target best torque AFR's. On the Sm2 one has to compromise on the ignition advance because that is only load/rpm based. The SM4 would be nicer for this...


            • #7
              Thank you for a wery good answer!

              I am looking forward to hear from you after the power tuning!

              Are you interrested to share the cal file you are using? I can also send my file..
              Saab 900 t16 Autronic SMC ++


              • #8
                this is also an intersting graph, it correlates well with my test.

                on the graph below I don't know if the ethanol curve is 100% ethanol (i think it is) or E85. ALso the x-axis is not Lambda, but the inverse of Lambda . SO richer is to the right.

                if you study the ethanol line between about .85 -1 FAR you can see that it is linear. This makes me think that that the difference in BSFC for any FAR/AFR in this range will be nearly the same.. Because less fuel is used when leaner,but more timing advance will be needed therefore more negative work. However because you will also have to open the throttle further to injest the same BTU's worth of fuel, pumping losses will less on the leftmost end of that linear range.


                • #9
                  In my experience I was able to run leaner (lamda) on E85 vs. standard pump gas without detonation, but leaning the mix out didn't make much difference in power so I saw no reason to remove that margin of safety in most applications. This pertains to high load areas only...

                  Originally posted by roberto arano View Post
                  That is to say mean best timing is less with e85, but less retard is needed to prevent knock.
                  This is exactly what I found when comparing to standard pump gas.
                  Last edited by Innovative Tuning; February 23rd, 2008, 11:17 PM.
                  Mike McGinnis


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